Unless otherwise indicated herein, the materials described in this section are not prior art to the claims in this application and are not admitted to be prior art by inclusion in this section.
Safety issues are a concern for robotic devices that operate in an unstructured environment, and share workspaces with human users and other objects. Contact by the robotic devices with other objects may be avoided by anticipating when and where such contact may occur.
Many robotic devices include compliant components that may allow for external contact with objects, and allow for deviations from an equilibrium position depending on the applied external force. An equilibrium position of a compliant component may be a position where the component generates zero force or zero torque. Some examples of compliant components include passive compliant actuators that contain an elastic element, such as a spring, that can store energy. Such an example passive compliant component includes a series elastic actuator SEA, which is a spring in series with a stiff actuator. Compliance of the actuator is fixed and is determined by selection of the spring. To obtain variable stiffness, a virtual stiffness of the actuator can be adjusted by dynamically adjusting the equilibrium position of the spring, for example.
In contrast, other robotic devices may include non-compliant components, in which a component is a stiff component and is able to move to a specific position or to track a predefined trajectory. Once a position is reached, the non-compliant component typically remains at that position despite any external forces exerted on the component (within force limits of the device, for example).
Other example robotic devices may be operated in ways that include motion planning or other control strategies for minimizing contact with objects. Such robotic devices may include sensors and controllers that operate according to algorithms to precisely control motion of components of the robotic device in predictable manners.